Safety coupling for shafts



Jan. 9, 1951 C F, DESMOND 2,537,122

' SAFETY CUPLING FOR SHAFTS Filed July 23, 1948-.

\ jaar Y Y if Charles F. vDesmond Patented Jan. 9, 1951 *U NITED :SAFETY CO'IPLING 'FR 'SHAFIS :Charles `lrF. "Desmmfid, Corfu, N. Y., assigner to HoudailleeHershey' Corporation, De'troit,lMich., `--a fcorporationiof :Michigan Application `July23, 1948, 'Serial No.4.0,343

9 Claims. 1

"This invention-:relatescto a .coupling .for rotatf able v4shaft-llike fmem'berspand. particularly :to-:a coupling rwhich Ywill automatically :prevent the transmission offan excessive torque between the coupledshaitlike members.

'While not limite'clilthereto, :this invention-.finds particular application in effectingthe coupling of a flexible shaft to a rotatable element. lThere are many applications Vin industry wherein a f shaft, gear, dial, .wheel or other :rotatable @member is ldisposed Awithinia vvcasing orzhousing andit is Ydesired Ato rotatably-drive :such rotatable memvber from a distance through the medium .oza Yflexible shaft. `As is .well known, any 'flexible `shaithas relativelyzlow torque transmitting properties as Vcompared fwith farigid shaft. ,Asza resu1t,`it"is possible for iian'funskilled operator to Accordingly, :it is :an-.object fof `the present invention to prcvideran improved safety coupling for rotatable shaft-like :members 'which will corotatably secure such-*members under normal `conditions ibut'which will automatically interrupt the fdriving connection :between-such members upon the occurrence of :a predetermined vmaximum torquetherebetween.

It `is an l -important:=object= of ethisainvention-V to `provide a -safety Vcoupling construction for shaftlike members `rcharacterized by unusualzsimplicity `of theicomponents .thereofand the ease ofmanu- "facture .and assemblage 4of such coupling.

A particular object `:of the invention; is `:tol -provide a `,safety coupling .formed-in vrits-:lentiretyf by the assemblage .of-three elements,.respectively :a female element, .a nmale :element `receivable :in

nested relationshipgwithpthe femaleelement,` land `a springof rthel-splitring type which vis carried by the male -elementfand is r.esiliently.iengageable .in cooperating 'grooves in the female element to vmaintain a driving -connection v.between the male and female elements yexcept when l an v.excessive torque occurstherebe'tween.

Still another object-of thefinvention is;to"pro vide a-n "improved, coupling construction particularlyv adaptableator" eiecting the .fsecurementtof a 4iiexible shaft to a rotatableV elementxdispcsed I Within a housing.

The specific-nature of .the inventiomfaas awe-liras other objects V'and advantages vthereof, will becomeapparenttothose ski-lledn the art fromithe follow-ing detailed description :of fthe annexed sheet of drawings `which,'by way of 4prefierrediexample only, illustrate Ione vfspec'iiflc embodiment `of the invention.

lOn the drawings: vFigure l a'sectionalview takenthroujghan Aasen'iloled coupling iarrangement embodyingthis invention.

cured-tothe stubshaft I Ibasbyvhavingapress-t engagementf'therewith. .The :female .coupling ele- Figure 3 :is :gansexploded 1secti0nalview iof the @elements assembled-inFigure. 1.

As Vshown.onthe drawings As Ypreviously indicated, this finventgion rfinds :particular:utility in .effecting the lcoupling :Ofxa lexible shaft to a 'rotatable element .disposed l.within"the interior vzoff a housing. T henurneral -,I 0 inthe drawings refers to-:a portionof .-snch'zfa "housingywhile .theznumeral II indicates/a rotatabler` element disposed within the housingwhch is toA be .drivenby or todrive a ilexible'fshaftnyidicated bythenumerallllZ. .'Ehehousing 1;!) Ais :provided with an integral bearingV hub :portion laila which .denesia bore llbgtheret-hrough-which is counterborecl at"Izcandsagainlat fllld. "The :counterhoreifi iid is .provided eintennalthreads.

vnlihevdrven;elementi I .disposedl within thehous- `y ing I0 .is hereillustratedasA a gear flliaewhichsis .':isuitabiyigrigidly :secured lv.fito a @stubfshaft `:portion The Velements lofla coupling embodying :this invention compriseirespectivelysa femalecouplng Velement I3, yaimale'couplingfelement` I4, and-.a .connecting springs-element I 5.

The female coupling element il 3 is of'generally cup-shaped conguration :having a ibase zportion Iu of substantial thickness'avhich.,'i5:centrally apertured'as indicatedlat vI 3b .and co-rotatably sement' I3 is journaled in the 'firstcoimterbore I'Iic 10i` the :bearing hub 'tarand `rests :upon ythe vshoulcler ldefined :between the juncture of. the S-bore 'I Ilb .sand the counterborea'Iac. liar-fluid seal is requiredbetween the inside and outside of lhousing Ill, an annular groove -I3c may-'be formed -inthe periphery of the base-portion *13a of the vfemale Avcoupling element andasealing ring I6 o fisu'itab1emateria1-mounted therein to eiiect .alsealing engagement with vthe Walls of ,Counterborelllm rThe annular wall portion .ld y.of .the Afemale coupling element .t3 ,projectsfinto .the largest counterbore VI iid .of rthe ,bearing Vhub I 0a. Avgpa-ir of .diametra'lly..o ,ppose.dy .axially extending jgrooves .or `recesses i3e are formed ,in the innersurfaoeiof the peripheral -wallfIdHfor-a purpose that will Vbedescribed.

.male coupling element 'IL4 .iszofi cylindrical, :bolt-.like coniiguration havingffan enlarged "head .portion Yi da which :is freely'f-yetsnugly; inserta-ble .within zathe :cylindrical recess ede'lned liby ithe peripheral Twall Ai3d of fthe female coupling element :13. In laddition;` thevmale fcoupling ele- "ment il 4 has a centrally frecesse'd,f-reduced `diame- \-l/ter stemffportionib in which vvis lsuitablyrigidly 'secured the-shaft core l2a1of' thefiexible-rshaft -'I2. *The iiexibleshaft l'l 2 "also embodies-a -survrounding helical iwire -casirlig "I lb fin'fconventional iifashion.

The head portion Illa of the male coupling element I4 is provided with a diametrally disposed, axially extending slot Illd which is of sub stantially the same depth as the annular wall portion I3d of the female coupling element I3. A spring element I5 is then mounted in the slot I4d and is so constructed that portions thereof, indicated at I5a, tend to project radially beyond the periphery of the head portion Ma of the male coupling element I4 to engage in the axially extending grooves I3e formed in the female coupling element. In this manner, a driving connection is established between the male and female coupling elements. However, the spring I5 is further constructed and proportioned so that upon the occurrence of a predetermined torque between the male and female coupling elements, such spring will be cammed inwardly or compressed by the action of the side walls I3f of the grooves I3e s0 as to disengage from such grooves and thus interrupt the driving connection between the male and female coupling elements. Such action of the spring I5 is most conveniently obtainedby forming such spring from resilient wire, shaped as a split ring element. To facilitate the camming action of the grooves I3e upon the spring I5, the side walls I3f of such grooves are preferably formed with a non-radial, generally inclined configuration.

To retain the male coupling element id in its inserted relationship with respect to the female coupling element I3, a retainer sleeve I'I is provided which is exteriorly threaded to permit it to be secured in the threaded counterbore Id of the bearing hub Iva. 'I'he sleeve I'I is provided with a central bore IIa of sucient diameter to freely accommodate the flexible shaft I2 and the stem portion I4b of the male coupling element I4. The bore I'Ia is counterbored at I'ib so as to freely surround the head portion Ilia of the male coup-ling element I4, and further `counterbored as at I Ic so as to freely surround the peripheral walls ISd of the female coupling element I3. The shoulder I'Id formed at the juncture of counterbore I'Ic and counterbore IIb cooperate with the end face of the female coupling element to retain such against axial movement, while the shoulder He formed at the juncture of counterbore I'Ib and bore I la cooperates with the shoulder I4e, defined between the head portion Illa and stem portion Ilib of the male couelement Ic against axial movement and thus retain it in nested assemblage with the female coupling element i 3.

The operation of the described coupling is believed to be obvious from the foregoing description. For transmission of torques up to a predetermined maximum, the male and female coupling elements are co-rotatably secured together by the split ring spring I5. When the transmitted torque exceeds a predetermined value, then the inwardly directed component of force exerted upon the ring spring I5 by the inclined wall surfaces I3f of the grooves I3@ overcomes f the resilient bias of the ring spring I5 and compresses such ring spring inwardly so that the portions I5a are no longer engaged in the grooves I3e in the female coupling element. Hence the driving connection between the male and female coupling elements is immediately interrupted,thereby precluding all possibility of damage to either the flexible shaft I2, or to gear Il, or any associated mechanism. When the transmitted torque falls below the predetermined value, the ring spring vpling element I4, to restrain the male coupling l I5 will immediately snap outwardly into engagement with the grooves I3e and re-establish the driving connection between the male and female coupling elements.

It should be particularly noted that the described construction embodies only three principal parts each of which is of unusually simple configuration, permitting the economical manufacture thereof in large quantities by automatic machinery. Furthermore, the assemblage of the coupling elements is unusually convenient and requires no special tools or skill.

It will, of course, be understood that various details of construction may be modified through a wide range without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

I claim as my invention:

1. A connector for a pair of rotatable shaftlike members disposed with the ends thereof in axial alignment, comprising a hollow female element adapted to be co-rotatably secured to one of said members, a male element adapted to be rotatably secured to said other member, said male element having at least a portion thereof inserted in said female element in nesting relation, said female element having an axailly extending groove in its bore surface, and a ring spring mounted in said inserted portion of said male member and radially engaging said groove, whereby said male and female elements are secured for co-rotation, said spring being resiliently deformable out of said groove upon occurrence of a predetermined torque between said male and female elements,

2. A connector for a pair of rotatablel shaftlike members disposed with the ends thereof in axial alignment, comprising a female element adapted to be co-rotatably secured to one of said members, a male element adapted to be rotatably secured to said other member, said male element having at least a portion thereof inserted in said female element in nesting relation, said female element having a recess adjacent said inserted portion of the male element, said male element having an axially extending slot therein, and a ring spring mounted in said slot and projecting radially therefrom to positively engage in said recess of the female element in the nested position of said male and female elements, said spring being resiliently deformable out of said recess upon the occurrence of `a predetermined torque between said male and female elements.

3. A connector for a pair of rotatable shaftlike members disposed with the ends thereof in axial alignment, comprising a hollow female element adapted to be co-rotatably secured to one of said members, a male element adapted to be co-rotatably secured to said other member, said male element having at least a portion thereof disposed in said female element in nesting relation, said female element having a pair of diametrically opposed, axially extending grooves in its bore surface, said male element having a diametral, axially extending slot therein, and a wire ring spring mounted in said slot and having opposed sides vprojecting radially out of said slot to respectively engage in said grooves of said female element, said wire spring being resiliently compressible to be forced out of said grooves of the female element upon occurrence of a predetermined torque between said male and female elements.

4. A connector for a pair of rotatable shaftlike members disposed with the ends thereof in axial alignment, comprising a hollow female element adapted to be co-rotatably secured Vto one of said members, a male element adapted to be co-rotatably secured to said other member, said male element having at least a portion thereof disposed in said female element in nesting relation, said female element having a pair of diametrically opposed, axially extending grooves in its bore surface, said male element having a diametral, axially extending slot therein, and a wire ring spring projecting radially out of said slot to respectively engage in said grooves of said female element, said grooves having generally inclined side walls, said inclined side walls of said grooves being constructed and arranged to resiliently compress said spring to displace the same from said grooves upon the occurrence of a predetermined torque between said male and female coupling elements.

5. A rotational coupling comprising a bearing housing defining a bore and a counterbore, a female coupling element journaled in said bore, means on said female coupling element for corotatably engaging a f-lrst rotatable member, a male coupling element axially insertable in said female coupling element, said female coupling element having an axially extending groove in its bore surface, a spring mounted in said in serted portion of said male coupling element and engaging said groove, whereby said male and female elements are co-rotatably secured, said spring being resiliently deformable out of said groove upon the occurrence of a predetermined torque between said male and female coupling elements, a retaining sleeve surrounding said male coupling element and secured in said counterbore, and means on said retaining sleeve engageable with said male coupling element to prevent axial removal of said male coupling element from nested engagement with said female coupling element. f

6. A rotational coupling comprising a bearing housing defining a bore and a counterbore, a hollow female coupling element journaled in said bore, means on said female coupling element for co-rotatably engaging a first rotatable member, a male coupling element axially insertable in said female coupling element, said female coupling element having a pair of diametrically opposed, axially extending grooves in its bore surface, said male coupling element having a diametral, axially extending slot in its inserted portion, a split wire ring spring mounted in said slot and having opposed sides thereof projecting radially out of said slot to respectively engage in said grooves y in the female coupling element, said grooves having generally inclined side walls so as to exert a camming action on said spring to displace said spring out of said grooves upon the occurrenceV of a predetermined torque between said male and female coupling elements, a retaining sleeve surrounding said maley coupling element and secured in said counterbore, and means on said retaining sleeve engageable with said male coupling element to prevent axial removal of said male coupling element from nested engagement with said female coupling element.

7. A rotational coupling comprising a cupshaped element secured to a first rotatable member, said cup-shaped element having an axially extending recess in the inner peripheral wall surface thereof, a plug element secured to a second rotatable member, said plug element having a portion thereof freely insertable within said cupshaped element, said insertable portion of the plug element having an axially extending slot therein opening in at least one side of the peripheral surface of said cylindrical portion, a, split ring spring mounted in said slot and having a portion thereof normally projecting out of said slot and engageable in said recess, whereby said plug element and said cup-shaped element are co-rotatably connected, said ring spring being resiliently compressible to lie entirely within said slot of the plug element, and the walls of said grooves being inclined to exert a compressing action on said split ring spring, whereby when excessive torque is applied to one of said rotatable members said inclined walls compress said ring spring within said slot to interrupt the driving connection between said plug and said cup shaped element.

8. A rotational coupling comprising a cup-l shaped element adapted to be secured to a rst rotatable member, said cup-shaped element having a pair of diametrically opposed, axially extending recesses in the inner peripheral wall thereof, a plug element adapted to be secured to a second rotatable member, said plug element having a cylindrical portion snugly insertable in said cup-shaped element, said cylindrical portion of the plug element having a, diametral, axially extending slot therein opening through both sides of the peripheral surface of said cylindrical portion, a split ring spring mounted in said slot, the unstressed configuration of said spring being constructed and arranged so that portions thereof normally project radially out of both sides of said slot to respectively engage in said recesses in said cup-shaped element whereby said plug element and said cup-shaped element are co-rotatably connected, said split ring springbeing resiliently compressible to lie entirely within the confines of said plug element, and the walls of said recesses being inclined to exert a, camming action on the engaging portions of said split ring spring to displace said spring out of said recesses upon the occurrence of a predetermined torque between said cup-shaped element and said plug element, whereby the driving connection between said elements is interrupted.

9. A rotational coupling comprising freely interfitting male and female members relatively rotatable except when coupled, said female member having a longitudinally extending recess and said male member having a cooperating longitudinal slot, and a contractible split ring of resilient material partially confined in said slot and having a closed loop portion normally extending into said recess to co-rotatably couple said members but contractible out of said recess upon the occurrence of a predetermined torque between said members to release said members for relative rotation.

CHARLES F. DESMOND.

REFERENCES CITED The following references are of record in the ,file of this patent:

UNITED STATES PATENTS Number Name Date 1,320,582 Sperling Nov. 4, 1919 1,468,322 Odom Sept. 13, 1923 1,831,317 Norris Nov. 10, 1931 2,259,797 Cohen Oct. 21, 1941 2,441,038 .Siesel May 4, 1948 

